Control operating mechanism



July lo, 1945. w. TYDON ET AL v 2,379,999

CONTROL OPERATING MECHANISM Filed Jan. 31, 1941 I v INVENTORS WALTERTYDON AND BY WINFIELD J-AUGUfiTINF ATTORNEY Patented July 10, 1945UNITED STATES, PATENT OFFICE I CONTROL G MECHANISM I Walter Tydon,Kenmore, and Winfield J. Augustine, Hempstead, N. Y., assignors toGui-tiss- Wright Corporation, a corporation of Delaware ApplicationJanuary 31, 1941, Serial No. 316,748

4 Claims. (01. 244-87) This invention relates to aircraft and is particularly concerned with improvements in operating mechanism for controlsurfaces thereof,

In modern aircraft, devices variously known as ternate mode ofindicating the adjusted position of a trim tab.

Referring first to Figs. 2 and 3, we show a support structure III whichmay comprise a fixed stabilizing airfoil at the empennage of theaircraft or alternately, this may comprise one of the main wings. To thetrailing edge of the support I is hinged a movable control airfoil II,

on an axis l2, and controlled movement of this airfoil is accomplishedthrough a push-pull rod trim tabs or Flettner balances, are used for thel3 clevised to ahorn l4 fixed to the airfoil. The purpose of trimmingthe aircraft longitudinally airfoil ll includesafront spar-l5 adjacentto the or directionally. Such tabs are hinged to the hinge l2, and theairfoil covering embraces this a rearward portions of the horizontalcontrol surp r f min a l adin e e It forward of the faces orstabilizers, or 'to the vertical control hinge I2 and masked by thetrailing edge of the surfaces or rudders, and are usually controllablesupport "I. Close to the trailing edge of the airfrom the pilots cockpitby cable connections or foil II, a trim tab I1 is hinged on an axis I8,the some form of mechanical operating means. As tab having a horn l9hinged to a push-pull rod the air controls are simplified, it becomesdesir- 2 ex en ing hrough p rt 2| in the airfoil covable to minimizeextended mechanical moving ering to a bell crank 22 hinged at 23 to a bac et devices, with a possible exception of the main air 24 S c red tohe Spar IS. The bellcrank 22 excontrols such as the elevators, rudders,or ailertends through an apertu e in t e spa d is ons and it isaccordingly an object of this in loosely connected to a nut 26 embracinga screw vention to provide remote control means for trim Shaft 21journalled at its right end in a bearing tabs wherein control movementof the trim tab 28 d driv n at i s lef en b" a motor 29 is accomplishedby means of an electric motor through a reduction gear 30. The nut 26carries disposed close to the tab, and whereby the control n t s n 32 ena a w th utt ns 33 f system for the motor comprises merely a pair oflimit switches 34 secured within the leading e conductors extending fromthe pilots quarters toof the airfoil. As will shortly be described inward the control airfoils and tabs. connection with the wiring diagram,the motor A further object is toprovide means for limit- 29 may beenergized to traverse the nut 26 along ing the angular movement of thetrim tabs while the screw 2 which, t u h t bellcrank. an additionalobject is to provide electrical means moves the i tab to one Side theother for indicating the adjusted position of trim tabs of the centralplane of the airfoil II. when the at any time. tab l1 moves to eitherextreme position, the nut A further object consists in disposin th powerextension 32 engages one or the other of the limit device and mechanicaltransmission for adjustswitch buttons 33 to de-energize the motor 29.ing a trim tab in such a position in a movable Along the front face of tSp a @180- control airfoil that it wei ht tt in an dtrical resistor 36is secured and the nut 26 carries vantageous function aerodynamically.Still ana sliding contact arm 38 engaging the surface of other object is'to provide a transmission mechathe resistor. nism, disposed within amovable airfoil, for the N W eferring to Fig. 1, the heavy wiringindipurpose of adjusting a trim tab hinged t the cates the power circuitfor the motor 29, this cirmovable airfoil. cuit including a power source40 grounded at one Further objects will be appreciated in reading sideand connected at its other side to a switch the annexed description inconnection with the 40 arm 4| selectively engageable with either of twodrawing, in which: 7 contacts 42 or 43 respectively connected to oneFig. 1 is a wiring diagram for the electrical or the other of the limitswitches 34, these in trim tab control system of the invention; turnbeing connected to the forward and reverse Fig. 2 is a plan of anaircraft movable control field windings 45 and 46 provided in theelectric surface, partly broken away, to show the op- 45 m t r 9, t s win be s ri lly connected erating mechanism foratrim tab; with the motorarmature whose opposite ter- Fig. 3 is a section on the line 33 of Fig.2; minal is grounded. If an operator desires to and move the trim tab I!to one side or the other, Fig. 4 is a simplified wiring diagram for anal- 50 he closes the switch arm 4| on the point 42 or the point 43,which will energize the motor 29 for forward or reverse rotation withresultant move of the trim tab. When the trim tab reaches a limitingposition, the nut extension 26 will contact the limit switch button 33to open the motor energizing circuit previously closed; closure of themotor circuit for the other direction of rotationwill cause reverserotation of the motor since the limit switch 34 for the other directionof rotation is closed.

For indicating the position of the trim tab, an ammeter 50 is installedin the cockpit, this-bein serially connected with the power source, theresistor 36, the sliding contact 38, and ground. As H the nut 26 movesalong the screw shaft 21, the resistance of the resistor 36 will bechanged proportionally so that the ammeter 50 may be directly calibratedto indicate degrees of trim tab displacement from either side ofneutral.

Fig. 4 shows an alternate arrangement wherein the ammeter 50 is replacedwith a voltmeter 50 whose terminals are connected with one end of theresistor, or potentiometer, in this case, 36' and to the slider 38'. Thetwo ends of the potentiometer resistance 36' areconnected across thebattery. Thus, the voltmeter will register a voltage drop across thepotentiometer whichis proportional to the position of the trim tab andthe voltmeter, like the ammeter 50, may be calibrated in degrees of trimtab displacement from neutral.

Returning again to Fig. 3, it will be noted that the motor 29 and screwshaft 21, along with the bulk of the power mechanism for adjusting thetrim tab, is disposed ahead of the airfoil hinge axis l2 and lies whollywithin the confines of the airfoil. The mechanism thus assists instatically balancing the airfoil I I about its hinge axis to the endthat fluttering tendency in the airfoil is suppressed. The teaching ofstatically balancing, or over-balancing, an airfoil is old in the artbut in this instance the balancing may be accomplished by usefulmechanism in the airfoil leading edge rather than by the use of deadweight.

While we have described our invention in detail in its present preferredembodiment, it will be obvious to those skilled in the art, afterunderstanding our invention, that various changes and modifications maybe made therein without departing from the spirit or scope thereof. Weaim in the appended claims to cover all such modifications and changes.

We claim as our invention:

1. In aircraft controls, in combination, a fixed airfoil, a manuallycontrollable airfoil hinged to the trailing edge thereof about anormally horizontal axis rearwardly spaced from but relatively close tothe leading edge of the controllable airasraeaa foil, a trim tab hingedto the rear edge of the controllable airfoil, an electric motor intheleading edge of the controllable airfoil ahead of said hinge axis sothat the motor assists in statically balancing the controllable airfoil,a mechanical transmission connecting the motor and trim tab to translatemotor operation into tab movement with respect to the controllableairfoil, and a selectively operable electric circuit for energizing saidmotor.

2. In an aircraft, a manually controllable airfoil hinged to a supportabout a normally horizontal axis disposed relatively close to butrearwardly spaced from the leading edge of said airfoil, a trim tabhinged to the rear edge of the controllable airfoil, an electric motorin the leading edge of the controllable airfoil having a screw shaftrotated thereby, a non-rotating nut movable along the screw shaft uponrotation thereof, means connecting the nut to the trim tab for operationof the trim tab thereby relative to said controllable airfoil, saidelectric motor, screw shaft and nut all being located in thecontrollable airfoil ahead of said hinge axis so that these elementsassist in statically balancing the controllable airfoil.

3. In an aircraft, a support, an adjustable airfoil hinged thereto abouta normally horizontal axis disposed relatively close to but rearwardlyspaced from the leading edge of said airfoil, an auxiliary airfoilhinged to the trailing edge of said adjustable airfoil, a motor in theleading edge of said adjustable airfoil ahead of its hinge axis wherebythe motor assists in statically balancing the adjustable airfoil, andmeans operatively connecting said motor to the auxiliary airfoil foroperation of said auxiliary airfoil with respect to the adjustableairfoil.

4. In an aircraft, a support, an adjustable airfoil hinged thereto abouta normally horizontal axis disposed relatvely close to but spaced fromthe edge of said airfoil adjacent said support, an auxiliary airfoilhinged to the edge of said adjustable airfoil remote from said support,a motor disposed within said adjustable airfoil between said firstmentioned edge of said airfoil and said axis whereby said motor assistsin statically balancing said adjustable airfoil, and means opertivelyconnecting said motor to said auxiliary airfoil for operation of saidauxiliary airfoil with respect to said adjustable airfoil.

WALTER 'I'YDON. WINFIELD J. AUGUSTINE.

